1. Field of the Invention
This invention relates to germicidal compositions, and more particularly relates to iodine compositions which are not degraded during radiation sterilization or prolonged shelf life.
2. Background
Iodine is a well-known germicide with activity against a wide range of bacteria and viruses, and much effort has been directed to finding satisfactory vehicles for its administration. Carriers of iodine which are often used are termed iodophors. Iodophors are generally polymeric materials, such as surfactants and polyvinylpyrrolidone (povidone) which form complexes with iodine.
In some cases, an iodophor-iodine complex is impreqnated into a sponge or brush used for germicidal cleansing or scrubbing. Often, such implements are included in a kit of materials which may also include other items useful for patient preparation, such as towels, gloves and the like. Such kits must be sterilized at some time prior to their use, usually at the time of manufacture. Gamma radiation is an effective sterilizing process, however, irradiation is known to decrease significantly the quantity of available iodine by conversion to iodide ion with consequent reduction in antibacterial activity.
Other problems arise in the use of iodine as a germicide. A typical iodine product, whether sterilized or not, continuously loses iodine during its shelf life. Iodophors are generally used in an aqueous base, and, in the presence of water, iodine undergoes a well-known but complex series of reactions leading, among other species, to iodide ions and hydrogen ions. The production of hydrogen ions may reduce the pH of a topical iodine preparation enough to cause skin irritation and discomfort to the user. Loss of iodine titer causes an additional problem of assuring that the iodine content of a composition does not fall below the stated concentration on the label during its time on the shelf.
Accordingly, a variety of approaches has focused on ways to stabilize the iodine concentration in an iodophor-iodine complex. U.S. Pat. No. 4,271,149 to Winicov et al. discloses a germicidal iodine composition of stabilized iodine concentration. The composition contains an organic material, iodine, iodide ion and iodate ion and is maintained at a pH of from 5 to 7 wherein the iodide and iodate react in the presence of hydrogen ions to replenish iodine lost during storage.
U.S. Pat. No. 4,113,857 to Shetty discloses a method to stabilize a preformed iodophor-iodine complex by adding an oxidizing agent, such as iodate ion, and to prepare a complex by reacting an iodophor, such as povidone, with iodate and iodide ions.
An iodine-surfactant germicidal cleansing composition is disclosed in U.S. Pat. No. 4,597,975 to Woodward et al. In the Woodward et al. composition, low concentrations of iodine are stabilized as the triiodide salt by complexing with an amine oxide surfactant. When solubilized by excess amine oxide, the triiodide salt has a very low iodine vapor pressure and high germicidal activity.
Bunting et al., in U.S. Pat. No. 4,427,631, discloses a method to radiation-sterilize a povidone-iodine composition. Iodide ion and iodate ion are added to the composition prior to irradiation to prevent radiation-induced gelation of the povidone and radiation-induced decrease in the amount of available iodine.
Although the above disclosures have improved iodophor stability during sterilization and shelf time, there remains a need for further improvement, particularly during a prolonged shelf life. It is toward fulfillment of this need that the present invention is directed.